According to a message on one of the development mailing lists, Google seems to be planning a beta of Chrome to appear sometime in December. There isn't any set date, and the message wasn't even addressing the release of a beta for Mac, but Nick Baum, a Google Chrome product manager, also the author of the mailing list post, let word fly. "Why make the switch now? The earlier you switch, the more time you will have
to polish your experience for our Beta launch in early December. We realize
this means dropping Mac support for a couple of weeks, but we already have
people working on that. If you prioritize the Windows and Linux versions,
we'll bring you cross-platform parity as soon as we can!"